Messages in this thread Patch in this message | | | Date | Thu, 29 Aug 2013 13:42:35 -0700 | From | "tip-bot for H. Peter Anvin" <> | Subject | [tip:x86/asm] x86, doc: Update uaccess.h comment to reflect clang changes |
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Commit-ID: f69fa9a91f60fff6f2d8b658b7d84d235d9d89b7 Gitweb: http://git.kernel.org/tip/f69fa9a91f60fff6f2d8b658b7d84d235d9d89b7 Author: H. Peter Anvin <hpa@linux.intel.com> AuthorDate: Thu, 29 Aug 2013 13:34:50 -0700 Committer: H. Peter Anvin <hpa@linux.intel.com> CommitDate: Thu, 29 Aug 2013 13:34:50 -0700
x86, doc: Update uaccess.h comment to reflect clang changes
Update comment in uaccess.h to reflect the changes for clang support: gcc only cares about the base register (most architectures don't encode the size of the operation in the operands like x86 does, and so it is treated effectively like a register number), whereas clang tries to enforce the size -- but not for register pairs.
Link: http://lkml.kernel.org/r/1377803585-5913-3-git-send-email-dl9pf@gmx.de Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: Jan-Simon Möller <dl9pf@gmx.de> --- arch/x86/include/asm/uaccess.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index f715fee..5838fa9 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -153,11 +153,14 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL)) * Careful: we have to cast the result to the type of the pointer * for sign reasons. * - * The use of %edx as the register specifier is a bit of a + * The use of _ASM_DX as the register specifier is a bit of a * simplification, as gcc only cares about it as the starting point * and not size: for a 64-bit value it will use %ecx:%edx on 32 bits * (%ecx being the next register in gcc's x86 register sequence), and * %rdx on 64 bits. + * + * Clang/LLVM cares about the size of the register, but still wants + * the base register for something that ends up being a pair. */ #define get_user(x, ptr) \ ({ \ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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